Is it possible to color-code the tabs on the toolshelf?
In blender's preferences for the 3DView theme settings, almost at the bottom, you will find the colours used for drawing the tabs.



This is a global property that is used by every tab and the only way blender offers to alter the tab panel colouring. You could adjust your theme so that the Tab Active and Tab Inactive colours are lighter so that there is more contrast with the text to make them easier to read.

In general blender doesn't offer ways to adjust the UI as far as colours go, almost every colour used is defined within a theme so that the UI stays consistant.